Signaling aspects for indication of co-scheduled DMRS ports in MU-MIMO

ABSTRACT

The present disclosure relates to a mobile terminal, a base station, a method for data transmission/reception by a mobile terminal, and a method for data reception/transmission by a base station. The mobile terminal comprises circuitry which, in operation, receives a parameter defining a configuration for assigning to ports respective resources for carrying reference signals, the resources being grouped in a plurality of code division multiplexing, CDM, groups, and receives control information indicating one of the set of layer-to-port mapping combinations which is to be applied for arranging reference signals on ports of at least one CDM group for data transmission and/or reception, wherein the control information indicates a co-scheduling information for the at least one and/or at least a different CDM group of the plurality of CDM groups for the same data transmission and/or reception.

BACKGROUND 1. Technical Field

The present disclosure relates to transmission and reception of dataand/or reference signals in resources of a communication system.

2. Description of Related Art

Currently, the 3^(rd) Generation Partnership Project (3GPP) works at thenext release (Release 15) of technical specifications for the nextgeneration cellular technology, which is also called fifth generation(5G). At the 3GPP Technical Specification Group (TSG) Radio Accessnetwork (RAN) meeting #71 (Gothenburg, March 2016), the first 5G studyitem, “Study on New Radio Access Technology” involving RAN1, RAN2, RAN3and RAN4 was approved and is expected to become the Release 15 work itemthat defines the first 5G standard.

One objective of 5G NR is to provide a single technical frameworkaddressing all usage scenarios, requirements and deployment scenariosdefined in 3GPP TSG RAN TR 38.913 v14.1.0, “Study on Scenarios andRequirements for Next Generation Access Technologies”, December 2016(available at www.3gpp.org), at least including enhanced mobilebroadband (eMBB), ultra-reliable low-latency communications (URLLC),massive machine type communication (mMTC).

For example, eMBB deployment scenarios may include indoor hotspot, denseurban, rural, urban macro and high speed; URLLC deployment scenarios mayinclude industrial control systems, mobile health care (remotemonitoring, diagnosis and treatment), real time control of vehicles,wide area monitoring and control systems for smart grids; mMTC mayinclude the scenarios with large number of devices with non-timecritical data transfers such as smart wearables and sensor networks.

Another objective is the forward compatibility. The backwardcompatibility to the Long Term Evolution (LTE) is not required, whichfacilitates a completely new system design and/or the introduction ofnovel features.

As summarized in one of the technical reports for the NR study item(3GPP TSG TR 38.801 v2.0.0, “Study on New Radio Access Technology; RadioAccess Architecture and Interfaces”, March 2017), the fundamentalphysical layer signal waveform will be based on Orthogonal FrequencyDivision Multiplexing (OFDM). For both downlink and uplink, OFDM withcyclic prefix (CP-OFDM) based waveform is supported. Discrete FourierTransformation (DFT) spread OFDM (DFT-S-OFDM) based waveform is alsosupported, complementary to CP-OFDM waveform at least for eMBB uplinkfor up to 40 GHz.

One of the design targets in NR is to seek the common waveform as muchas possible for downlink, uplink and sidelink. It has been consideredthat introduction of the DFT spreading might not be needed for somecases of uplink transmission. The term “downlink” refers tocommunication from a higher node to a lower node (e.g., from a basestation to a relay node or to a UE, from a relay node to a UE, or thelike). The term “uplink” refers to communication from a lower node tothe higher node (e.g., from a UE to a relay node or to a base station,from a relay node to a base station, or the like). The term “sidelink”refers to communication between nodes at the same level (e.g., betweentwo UEs, or between two relay nodes, or between two base stations).

The term spatial layer (or layer) refers to one of different streamsgenerated by spatial multiplexing. A layer can be described as a mappingof symbols onto the transmit antenna ports. Each layer is identified bya precoding vector of size equal to the number of transmit antenna portsand can be associated with a radiation pattern. The rank of thetransmission is the number of layers transmitted. A codeword is anindependently encoded data block, corresponding to a single TransportBlock (TB) delivered from the Medium Access Control (MAC) layer in thetransmitter to the physical layer, and protected with a cyclicredundancy check (CRC).

Generally, a layer is assigned per transmission time (TTI) intervalwhich in LTE corresponds to the subframe. However, in 3GPP NR, there canbe different TTIs, depending on URLLC or eMBB. In particular, in NR theTTI can be a slot, mini-slot, or subframe. For layers, ranks, andcodewords, see also section 11.2.2.2 of S. Sesia, I. Toufik and M,Baker, LTE: The UMTS Long Term Evolution, Second Edition.

Conventionally, a reference signal pattern (RS) is transmitted from anantenna port (or port) at the base station. A port may be transmittedeither as a single physical transmit antenna, or as a combination ofmultiple physical antenna elements. In either case, the signaltransmitted from each antenna port is not designed to be furtherdeconstructed by the UE receiver: the transmitted RS corresponding to agiven antenna port defines the antenna port from the point of view ofthe UE, and enables the UE to derive a channel estimate for all datatransmitted on that antenna port, regardless of whether it represents asingle radio channel from one physical antenna or a composite channelfrom a multiplicity of physical antenna elements together comprising theantenna port. For ports, see also section 8.2 of S. Sesia, I. Toufik andM, Baker, LTE: The UMTS Long Term Evolution, Second Edition.

In LTE, the data transmissions and receptions for a UE are scheduled bythe eNB by means of Physical Downlink Control Channel (PDCCH), whichcarries a message known as Downlink Control Information (DCI), whichincludes resource assignments and other control information for a UE orgroup of UEs. In general, several PDCCHs can be transmitted in asubframe.

The required content of the control channel messages depends on thesystem deployment and UE configuration. For example, if theinfrastructure does not support MIMO, or if a UE is configured in atransmission mode which does not involve MIMO, there is no need tosignal the parameters that are only required for MIMO transmissions. Inorder to minimize the signaling overhead, it is therefore desirable thatseveral different message formats are available, each containing theminimum payload required for a particular scenario. On the other hand,to avoid too much complexity in implementation and testing, it isdesirable not to specify too many formats. The set of DCI messageformats specified in LTE is listed below:

Please refer to the mentioned technical standard or to LTE—The UMTS LongTerm Evolution—From Theory to Practice, Edited by Stefanie Sesia, IssamToufik, Matthew Baker, Chapter 9.3.5.

-   -   Format 0: DCI Format 0 is used for the transmission of resource        grants for the PUSCH, using single-antenna port transmissions in        uplink transmission mode 1 or 2.    -   Format 1: DCI Format 1 is used for the transmission of resource        assignments for single codeword PDSCH transmissions (downlink        transmission modes 1, 2 and 7).    -   Format 1A: DCI Format 1A is used for compact signaling of        resource assignments for single codeword PDSCH transmissions,        and for allocating a dedicated preamble signature to a mobile        terminal for contention-free random access (for all        transmissions modes).    -   Format 1B: DCI Format 1B is used for compact signaling of        resource assignments for PDSCH transmissions using closed loop        precoding with rank-1 transmission (downlink transmission mode        6). The information transmitted is the same as in Format 1A, but        with the addition of an indicator of the precoding vector        applied for the PDSCH transmission.    -   Format 1C: DCI Format 1C is used for very compact transmission        of PDSCH assignments. When format 1C is used, the PDSCH        transmission is constrained to using QPSK modulation. This is        used, for example, for signaling paging messages and broadcast        system information messages.    -   Format 1D: DCI Format 1D is used for compact signaling of        resource assignments for PDSCH transmission using multi-user        MIMO. The information transmitted is the same as in Format 1B,        but instead of one of the bits of the precoding vector        indicators, there is a single bit to indicate whether a power        offset is applied to the data symbols. This feature is needed to        show whether or not the transmission power is shared between two        UEs. Future versions of LTE may extend this to the case of power        sharing between larger numbers of UEs.    -   Format 2: DCI Format 2 is used for the transmission of resource        assignments for PDSCH for closed-loop MIMO operation        (transmission mode 4).    -   Format 2A: DCI Format 2A is used for the transmission of        resource assignments for PDSCH for open-loop MIMO operation. The        information transmitted is the same as for Format 2, except that        if the eNodeB (name for a base station in LTE) has two transmit        antenna ports, there is no precoding information, and for four        antenna ports two bits are used to indicate the transmission        rank (transmission mode 3).    -   Format 2B: Introduced in Release 9 and is used for the        transmission of resource assignments for PDSCH for dual-layer        beamforming (transmission mode 8).    -   Format 2C: Introduced in Release 10 and is used for the        transmission of resource assignments for PDSCH for closed-loop        single-user or multi-user MIMO operation with up to 8 layers        (transmission mode 9).    -   Format 2D: introduced in Release 11 and used for up to 8 layer        transmissions; mainly used for COMP (Cooperative Multipoint)        (transmission mode 10)    -   Format 3 and 3A: DCI formats 3 and 3A are used for the        transmission of power control commands for PUCCH and PUSCH with        2-bit or 1-bit power adjustments respectively. These DCI formats        contain individual power control commands for a group of UEs.    -   Format 4: DCI format 4 is used for the scheduling of the PUSCH,        using closed-loop spatial multiplexing transmissions in uplink        transmission mode 2.

A search space indicates a set of CCE locations where the UE may findits PDCCHs. Each PDCCH carries one DCI and is identified by the RNTI(radio network temporary identity) implicitly encoded in the CRCattachment of the DCI. The UE monitors the CCEs of a configured searchspace(s) by blind decoding and checking the CRC. A search space may be acommon search space and a UE-specific search space. A UE is required tomonitor both common and UE-specific search spaces, which may beoverlapping. The common search space carries the DCIs that are commonfor all UEs such as system information (using the SI-RNTI), paging(P-RNTI), PRACH responses (RA-RNTI), or UL TPC commands(TPC-PUCCH/PUSCH-RNTI). The UE-specific search space can carry DCIs forUE-specific allocations using the UE's assigned C-RNTI, semi-persistentscheduling (SPS C-RNTI), or initial allocation (temporary C-RNTI).

A DCI thus specifies the resources on which a UE is to receive ortransmit data, including transmission and reception configuration.

BRIEF SUMMARY

One non-limiting and exemplary embodiment facilitates the signaling ofco-scheduling information (non-transparent MU-MIMO) on a percode-division multiplexing, CDM, group basis in a mobile communicationsystem where data is transmitted and/or received in layers usingmultiple antennas. More particularly, the present disclosure suggestssets of layer-to-port mapping combination which are combined withco-scheduling information to facilitate a more efficient and effectivesignaling mechanism.

In an embodiment, the techniques disclosed here feature a mobileterminal comprising circuitry which, in operation, receives a parameterdefining a configuration for assigning to ports respective resources forcarrying reference signals, the resources being grouped in a pluralityof code division multiplexing, CDM, groups, and receives controlinformation indicating one of the set of layer-to-port mappingcombinations which is to be applied for arranging reference signals onports of at least one CDM group for data transmission and/or reception,wherein the control information indicates a co-scheduling informationfor the at least one and/or at least a different CDM group of theplurality of CDM groups for the same data transmission and/or reception,and a transceiver which, in operation, performs transmission and/orreception data in layers using multiple antennas based on theco-scheduling information.

It should be noted that general or specific embodiments may beimplemented as a system, a method, an integrated circuit, a computerprogram, a storage medium, or any selective combination thereof.

Additional benefits and advantages of the disclosed embodiments willbecome apparent from the specification and drawings. The benefits and/oradvantages may be individually obtained by the various embodiments andfeatures of the specification and drawings, which need not all beprovided in order to obtain one or more of such benefits and/oradvantages.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIGS. 1A to 1D are schematic drawings of front loaded demodulationreference signal (DMRS) configuration types.

FIG. 2 is a block diagram showing the structure of a mobile terminal anda base station.

FIG. 3 shows an exemplary set of layer-to-port mapping combinationscombined with co-scheduling information on a per CDM group basis for aDMRS configuration type 1, and 1-symbol DMRS configuration;

FIG. 4 shows an exemplary set of layer-to-port mapping combinationscombined with co-scheduling information on a per CDM group basis for aDMRS configuration type 1, and 2-symbol DMRS configuration;

FIG. 5 shows an exemplary set of layer-to-port mapping combinationscombined with co-scheduling information on a per CDM group basis for thecase of a DMRS configuration type 2, and 1-symbol DMRS; and

FIGS. 6 a and 6 b show exemplary set of layer-to-port mappingcombinations combined with co-scheduling information on a per CDM groupbasis for the case of a DMRS configuration type 2, and 2-symbol DMRS.

DETAILED DESCRIPTION

In 3^(rd) generation partnership project new radio (3GPP NR), referencesignals are re-designed to meet the wide range of requirements and usecases. Demodulation reference signals (DMRS) that are used for thepurpose of channel estimation are also being designed to have a uniformstructure for both uplink and downlink with cyclic-prefix orthogonalfrequency division multiplexing (CP-OFDM) waveform. This disclosurerelates to the signaling aspects for supporting non-transparentMulti-User Multiple Input Multiple Output (MU-MIMO). Two configurations(with different multiplexing schemes for orthogonal DMRS ports) offront-loaded DMRS will be supported and each configuration withflexibility of using 1-symbol or 2-symbol DMRS.

In current LTE, there is a fixed configuration with single category ofmultiplexing scheme for orthogonal DMRS ports and no support fornon-transparent MU-MIMO.

However, in 3GPP NR, the situation is more complex due to thepossibility of more interference from co-scheduled DMRS ports for otherUEs. In addition, rate matching is necessary due to frequency divisionmultiplexing (FDM) between different DMRS ports. Based on this, it isexpected to support UE non-transparent MU-MIMO in NR. In thisdisclosure, we provide a framework to indicate at least some informationabout the co-scheduled DMRS ports within same and/or different CDMgroups in MU-MIMO by adding new fields to the DMRS layer-to-port mappingtable.

This disclosure relates to NR technology. For NR access technology, see3GPP TSG RAN Meeting #75, RP-171485 by NTT DoCoMo, “Revised WID on NewRadio Access Technology”, Jun. 5-8, 2017). More specifically, it dealswith the aspects of front-loaded DMRS for both downlink and uplink withCP-OFDM waveform. In RAN1 NR #3 (RAN1 Chairman Notes: RAN1 NR Ad-Hoc#3), DMRS are captured and this provides a framework for signaling of atleast some information related to co-scheduled DMRS ports by using DMRSlayer-to-port mapping table.

As mentioned, in 3GPP NR, Demodulation Reference Signals (DMRS) arere-designed for both downlink and uplink.

Two configurations are supported for front-loaded DMRS in downlink anduplink with CP-OFDM waveform, which are illustrated in FIGS. 1A to 1D.

As shown therein, the front-loaded reference signals are allocated toresources of the first data symbol adjacent to resources for thesignaling section (the signaling section consisting of, e.g., twosymbols) of a TTI if one-symbol DMRS are used, and to resources of thefirst two data symbols if two-symbol DMRS are used.

FIGS. 1A to 1B each show an exemplary resource grid corresponding to aslot of 14 symbols and 12 subcarriers. The first two symbols on the leftof each of the figures correspond to the signaling section of a slot.The physical downlink control channel (PDCCH) is signaled in thesignaling section. In LTE, this exemplary resource grid would correspondto one of two slots of a subframe. However, this shall not limit thepresent disclosure since a subframe may also correspond to a (single)slot or include more than two slots; and the slot may also have more orless than 14 symbols and 12 subcarriers.

The first front-loaded DMRS configuration corresponding to configurationtype 1 is shown in FIGS. 1A and 1B. This configuration is aimed atsupporting up to eight orthogonal DMRS ports for Single-User MultipleInput Multiple Output (SU-MIMO) or Multi-User Multiple Input MultipleOutput (MU-MIMO). The first configuration supports up to four orthogonalDMRS ports if one symbol DMRS are used, as shown in FIG. 1A. Inparticular, two combs and two cyclic shifts (CS) may be combined to formup to four component sets, and the respective resulting component setscan be respectively assigned to up to four DMRS ports. These componentsets are in the context of the present disclosure also referred to asCDM groups.

If two symbol DMRS are used, as shown in FIG. 1B, the two combs and twocyclic shifts may be combined with two time division Orthogonal CoverCodes (TD-OCC) in particular Walsh-Hadamard TD-OCCs, ({1,1} and {1,−1}),and up to eight orthogonal DMRS ports may be supported. However, in thetwo-symbol DMRS case it should also be possible to schedule up to 4 DMRSports without using both {1,1} and {1,−1}.

The second front-loaded DMRS configuration corresponding toconfiguration type 2 is shown in FIGS. 1C and 1D. This configurationprovides support for up to twelve orthogonal ports for SU-MIMO orMU-MIMO. In particular, two (Walsh-Hadamard) frequency divisionOrthogonal Cover Codes (FD-OCC) respectively applied across adjacent REs(resource elements) in the frequency domain yield six component sets orCDM groups.

As can be seen from FIGS. 1C and 1D, with twelve subcarriers, pairs ofadjacent REs are grouped into three Frequency Division Multiplexing(FDM) groups. Accordingly, the six component sets result from twoFD-OCCs (both {1,1} and {1,−1}) applied respectively to the three FDMgroups. In the case of one symbol DMRS (FIG. 1C), the resulting sixrespective component sets can be assigned to up to six orthogonal DMRSports. In the case of two-symbol DMRS, these six component sets mayfurther be combined with two TD-OCCs resulting in a capability tosupport up to twelve orthogonal DMRS ports (FIG. 1D).

As described above with reference to FIGS. 1A to 1D, combs, cyclicshifts, FD-OCCs, FDMs, and TD-OCCs constitute resource components forreference signals, in particular front-loaded DMRS.

These resource components are combined in accordance with the first orthe second front-loaded DMRS configuration, and the resulting componentsets or CDM groups are respectively assigned to orthogonal DMRS ports.However, usage of two-symbol DMRS should be possible even for lowerranks. Not all component sets or CDM groups that are supported by aparticular configuration in the one-symbol or two symbol DMRS case needto be used for assignment of a port. In particular, also in thetwo-symbol case it should be possible to schedule up to 6 DMRS portswithout using both {1,1} and {1,−1}.

From a user equipment (UE) perspective, DMRS ports multiplexed byfrequency domain code division multiplexing (CDM) are quasi co-located.

It is still open for further study whether the front-load DMRSconfiguration type for a UE for UL and DL can be different or not.Moreover, if there are significant complexity/performance issuesinvolved in the above agreements, down-selection can still be discussed.

LTE DMRS Configuration

The DMRS configurations in 3GPP NR described above are different fromLTE, where there is a mainly a single configuration in downlink tosupport up to total 8 orthogonal ports/layers using code-divisionmultiplexing in frequency and time using Walsh-Hadamard orthogonal covercodes. The configuration and further details on the DMRS configurationsin LTE can be found in section 29.1.1 of S. Sesia, I. Toufik and M,Baker, LTE: The UMTS Long Term Evolution, Second Edition.

The table of layer-to port mapping in current LTE, which is taken from3GPP TS 36.212, V14.3.0 (Table 5.3.3.1.5C-2) is shown in the FollowingTable 1:

TABLE 1 Antenna port(s), scrambling identity (SCID) and number of layersindication One Codeword: Two Codewords: Codeword 0 enabled, Codeword 0enabled, Codeword 1 disabled Codeword 1 enabled Value Message ValueMessage 0 1 layer, port 7, n_(SCID) = 0 0 2 layer, port 7-8, n_(SCID) =0 (OCC = 2) (OCC = 2) 1 1 layer, port 7, n_(SCID) = 1 1 2 layer, port7-8, n_(SCID) = 1 (OCC = 2) (OCC = 2) 2 1 layer, port 8, n_(SCID) = 0 22 layer, port 7-8, n_(SCID) = 0 (OCC = 2) (OCC = 4) 3 1 layer, port 8,n_(SCID) = 1 3 2 layer, port 7-8, n_(SCID) = 1 (OCC = 2) (OCC = 4) 4 1layer, port 7, n_(SCID) = 0 4 2 layer, port 11, 13, (OCC = 4) n_(SCID) =0 (OCC = 4) 5 1 layer, port 7, n_(SCID) = 1 5 2 layer, port 11, 13, (OCC= 4) n_(SCID) = 1 (OCC = 4) 6 1 layer, port 8, n_(SCID) = 0 6 3 layer,port 7-9 (OCC = 4) 7 1 layer, port 8, n_(SCID) = 1 7 4 layer, port 7-10(OCC = 4) 8 1 layer, port 11, n_(SCID) = 0 8 5 layer, port 7-11 (OCC =4) 9 1 layer, port 11, n_(SCID) = 1 9 6 layer, port 7-12 (OCC = 4) 10 1layer, port 13, n_(SCID) = 0 10 7 layers, ports 7-13 (OCC = 4) 11 1layer, port 13, n_(SCID) = 1 11 8 layers, ports 7-14 (OCC = 4) 12 2layers, ports 7-8 12 Reserved 13 3 layers, ports 7-9 13 Reserved 14 4layers, ports 7-10 14 Reserved 15 Reserved 15 Reserved

In LTE, up to eight orthogonal DMRS ports for downlink are supported,which mainly use a single category of multiplexing scheme, OCC intime/frequency. Therefore, any of the port combinations could be usedfor mapping layers without impacting the performance for a givenscenario. Furthermore, for a given number of layers, usage of resources(DMRS overhead) is the same for any port combination.

Moreover, LTE provides limited support for MU-MIMO. Also, a fixed DMRSconfiguration is supported; hence no additional signaling is requiredfor dynamic configuration.

As can be seen from the Table 1, there are very limited combinationsallowed for layer-to-port mapping in LTE. A length 4 bitmap is definedto signal the layer-to-port mapping for a given user. A minimum numberof port combinations are supported for layer-to-port mapping resultsfrom the following restrictions. For up to two layers, port-indexing forthe mapping is consecutive and non-overlapping. For three to eightlayers, the indexing is consecutive, non-overlapping, and starting fromindex 0 as a fixed start point. The mapping is limited to one portcombination.

In the latest release of LTE only transparent MU-MIMO (and nonon-transparent MU-MIMO) is supported. However, this was not always thecase:

In LTE Rel-8, when MU-MIMO was introduced for the first time to supporttransmission up to 2 UEs, non-transparent MU-MIMO was introduced byhaving a 1-bit dedicated power offset field. Yet, support fornon-transparent MU-MIMO for more than two UEs was never agreed,particularly not in the later releases of LTE. The drawback of anincreased signaling overhead was decided not to outweigh the benefitsresulting therefrom.

DMRS Requirements for NR

The restrictions to the layer-to-port mapping of LTE are no longerbearable in 3GPP NR. Particularly, there is a demand for non-transparentMU-MIMO to benefit from the advantages of a new system design in 3GPPNR.

For example, for incorporating the support of non-transparent MU-MIMOinto 3GPP NR, it would be possible to revisit the decision taken for LTEof not incorporating dedicated bit fields. However, also under currentconsiderations, since there exists a dedicate bit field for MU-MIMO, thesupport is not necessary.

DESCRIPTION OF EMBODIMENTS

The present disclosure facilitates the signaling of co-schedulinginformation (non-transparent MU-MIMO) on a per code-divisionmultiplexing, CDM, group basis in a mobile communication system wheredata is transmitted and/or received in layers using multiple antennas.More particularly, the present disclosure suggests sets of layer-to-portmapping combination information which are combined with co-schedulinginformation to facilitate a more efficient and effective signalingmechanism.

In an exemplary embodiment, as shown in FIG. 2 , the present disclosureprovides a mobile terminal 210 for transmitting and/or receiving datato/from a base station 260 which uses multiple antennas in a mobilecommunication system. The mobile terminal 210 and the base station 260are configured to transmit and/or receive the data over a wirelesschannel 250.

The mobile terminal 210 may correspond to a user equipment (UE), as isusually named in LTE and NR, and the bases station 260 may correspond toan evolved NodeB (eNodeB or eNB) or a next generation NodeB (gNodeB orgNB), as is usually named in LTE and NR.

More particularly, the mobile terminal 210 is configured to transmitand/or receive the data in layers to/from the base station 260. Asdiscussed above, the term layer (or spatial layer) refers to one ofdifferent streams that are generated by spatial multiplexing and thenare exchanged between the mobile terminal 210 and the base station 260over different antenna ports.

For a coherent demodulation of the transmitted and (subsequently)received data, reference signals are also exchanged between the mobileterminal 210 and the base station 260. As discussed above, thetransmission and/or reception of reference signals is performed withreference to a layer-to-port mapping. This mapping specifies for each ofthe respective layers one DMRS port which is to be used fortransmitting/receiving the reference signals.

Notably, the layer-to-port mapping varies depending on a configurationof the base station 260 and the mobile terminal 210, namely aconfiguration specified by the DMRS configuration type (e.g., DMRSconfiguration type 1 or 2) and the number of symbols to be used for DMRS(e.g., one-symbol or two-symbol DMRS). As discussed above, thisconfiguration does not only determine the resources on which the DMRSare carried, but also the maximum number of DMRS ports that can bescheduled by the base station 260.

In other words, mobile terminal 210 and the base station 260 revert todifferent layer-to-port mappings depending on which one of pluralconfigurations is chosen for communicating in the mobile communicationsystem. The configuration of DMRS ports is specified so that the basestation 260 and the mobile terminal can make use of the layer-to-portmapping in order to carry out the data transmission and/or reception.

For this purpose, the mobile terminal 210 comprises circuitry, forexample transceiver 220, and processor 230, which, in operation,receives a parameter defining a configuration for assigning to DMRSports respective (time-frequency) resources for carrying referencesignals. In other words, the configuration assigns each of the referencesignal of one or more DMRS ports to specific resources, which may alsobe referred to as (resource) component sets.

The resources or (resource) component sets are grouped in a plurality ofcode division multiplexing, CDM, groups. Particularly, a code divisionmultiplexing, CDM, group specifies the resources or (resource) componentsets on which reference signals are carried for each of the DMRS ports,such that on each of the resources, or (resource) component sets, therecan be carried a maximum number of say 2 or 4 orthogonal referencesignals on respective DMRS ports of the same CDM group.

Referring to the example shown in FIG. 1A, the resources of two combs(comb1, comb2), each with two cyclic shifts (resulting in a set of twodifferent DMRS ports), are defining separate CDM groups (CDM group0, CDMgroup 1). For the example shown in FIG. 1B, the resources of two combs(comb1, comb2), each with two cyclic shifts and with two TD-OCCs(resulting in a set of four different DMRS ports), are defining separateCDM groups (CDM group0, CDM group 1).

Further, for the example shown in FIG. 1C, the resources of three FDMgroups (FDM1, FDM2, FDM3), each with two FD-OCCs (resulting in a set oftwo different DMRS ports), are defining separate CDM groups (CDM group0,CDM group1, CDM group 2). Finally, for the example shown in FIG. 1D, theresources of three FDM groups (FDM1, FDM2, FDM3), each with two FD-OCCsand two TD-OCCs (resulting in a set of four different DMRS ports), aredefining separate CDM groups (CDM group0, CDM group1, CDM group 2).

As already set out above, the (time-frequency) resources for carryingthe reference signals are grouped in a plurality of code divisionmultiplexing, CDM, groups. Particularly, in the context of the presentdisclosure, a CDM group refers to a set of DMRS ports that use the sameresources and are orthogonal to each other by using orthogonal covercodes (OCC) or code division multiplexing (CDM) in time and/orfrequency.

In the context of the present disclosure, reference is made to CDMgroups from the perspective of the mobile terminal 210. For the mobileterminal 210, a CDM group refers to resources or (resource) componentsets of DMRS ports which are quasi co-located.

Again to the exemplary embodiment, the circuitry of the mobile terminal210, for example transceiver 220, and processor 230, in operation,receives control information indicating one of the set of layer-to-portmapping combinations which is to be applied for arranging referencesignals on DMRS ports of at least one CDM group for data transmissionand/or reception.

The mobile station 210 can then utilize the indicated one of a set oflayer-to-port mapping combination to determine the DMRS port or portsand, on the basis of the configuration of the resources or (resource)component sets, determine for this DMRS port or ports the respectiveresources for the data transmission and/or reception. In other words,only in combination do the configuration and the indicated layer-to-portmapping allow for the data transmission and/or reception.

However, both the configuration parameters and the control informationare not received by the mobile terminal 210 at a same time. Rather, thebase station 260 may signal the configuration parameters on aninfrequent basis, for example via the Radio Resource Control, RRC;protocol, whereas the control information may be signaled together withscheduling information in a downlink control information, DCI, via thephysical downlink control channel, PDCCH.

Further to the exemplary embodiment, the received control informationis, however, not restricted to only indicate to the mobile terminal 210the one of the set of layer-to-port mapping configurations. Rather, thereceived control information additionally indicates to the mobileterminal 210 a co-scheduling information on a per CDM group basis.

This co-scheduling information may then be utilized for the same datatransmission and/or reception, namely to improve interferencecancellation and/or rate matching for the data transmission and/orreception of the same TTI.

Indicating co-scheduling information on a per CDM group basis providesan advantageous trade-off for non-transparent MU-MIMO signaling.Particularly, the indication of co-scheduling on a per CDM group basisattains the advantage of minimizing the signaling overhead with respectto an improved the interference cancellation and/or the adaptation ofrate matching for increasing the data transmission capacity.

In the following, a distinction is made between the indication ofco-scheduling information for CDM group or groups (henceforth referredto as first set of CDM groups) in which the mobile terminal 210 isscheduled to perform reference signal transmission and/or reception, andother CDM group or groups which are not scheduled for the mobileterminal 210 (referred to as second set of CDM groups). Thisdistinction, however, becomes even more apparent in view of theadvantages resulting from the co-scheduling information.

As mentioned above, the mobile terminal 210 can use the co-schedulingindication for improved interference cancellation.

In each CDM group, a base station may co-schedule different mobileterminals to assign reference signals to DMRS ports on same resources(of a same CDM group). Even though the DMRS ports are said to beorthogonal to each other in a CDM group, there may be leakage-effectsbetween the reference signals, resulting in deteriorated receptionquality of the reference signals. This interference may thus lead toinferior coherent demodulation capabilities for the data transmissionand/or reception.

Now, with the additional co-scheduling information on the per CDM groupbasis, the mobile station is aware of co-scheduling on CDM group(s),namely on the resources, which are also carrying its “own” referencesignals. Thus, with this additional co-scheduling information, themobile station can perform interference cancellation on the referencesignals, thereby improving the coherent demodulation capabilities.

Notably, the improved interference cancellation is however related toco-scheduling information in the CDM group(s) in which mobile terminal210 is scheduled to perform reference signal transmission and/orreception (the first set of CDM groups).

Furthermore, the mobile terminal 210 can use the co-scheduled indicationfor improved rate matching.

In each CDM group, a base station may schedule different mobileterminals to assign reference signals to DMRS ports on differentresources (e.g., of different CDM groups). Even though the scheduling ofDMRS ports of different CDM groups is optimal with regard to theirinterference properties, this scheduling blocks the mobile terminal fromre-using the different resources (out of context) for transmissionand/or reception of data.

In other words, information on the (actual) assignment of referencesignals on different resources (of different CDM groups) puts a mobileterminal into a position where it can decide to allocate to this(additional) different resources (of different CDM groups) symbolscarrying a data transmission and/or reception. It goes without sayingthat this increases the data transmission capacity in the respectiveTTI, hence necessitates an adapted rate matching to make use of theincrease in data transmission capacity.

Now, with the additional co-scheduling information on the per CDM groupbasis, the mobile station is aware of co-scheduling on different CDMgroup(s), namely on the resources, which are not carrying its “own”reference signals. With this additional co-scheduling information, themobile terminal can then determine whether or not it can re-use theseresources from the different CDM group(s) for data transmission and/orreception, which, however, requires an accordingly adapted rate matchingto the increase in data transmission capacity.

Notably, the improved rate matching for the data transmission and/orreception of the same TTI is however only related to co-schedulinginformation in the different CDM group(s) in which the mobile terminalis not scheduled to perform reference signal transmission and/orreception (the second set of CDM groups).

In summary, the advantages of an improved interference cancellation andadaptation of rate matching for increasing the data transmissioncapacity, both tie in with the presence of co-scheduling information ona per CDM group basis, however, may depend on whether co-scheduling isindicated for CDM group(s) on which the mobile terminal is scheduled toperform reference signal transmission (the first set of CDM groups) ornot (the second set of CDM groups).

Thus, it is already apparent from this disclosure that indication ofco-scheduling information already provides for advantageous effects,even if it is signaled not for all but only for a subset of theplurality of CDM groups.

In the context of the present disclosure, the co-scheduling informationis signaled on a per CDM group basis. This co-scheduling informationshall be understood as an indication to the mobile terminal that thebase station is co-scheduling a different mobile terminal on DMRS portsof respective resources of each of the CDM groups for reference signaltransmission and/or reception.

Depending on the CDM group for which the co-scheduling information isprovided, it may be advantageous to interpret the co-schedulinginformation differently:

Regarding the second set of CDM groups, the co-scheduling informationallows a mobile terminal to adapt the rate mating to benefit from anincrease in data transmission capacity. Notably, for this it is onlynecessary for the mobile terminal to know, if (or not) there is at leasta single different mobile terminal assigned to a DMRS port of thedifferent CDM group(s).

If in one of the second set of CDM groups there is at least a singleDMRS port assigned, then the respective reference signal transmissionand/or reception is considered more important than the adaptation ofrate matching and the benefit from an increase in data transmissioncapacity. Otherwise, the mobile terminal may adapt rate matching to takeadvantage increase in data transmission capacity thereof.

Thus, for the second set of CDM groups, the co-scheduling informationmay thus be interpreted as indicating “at least one” different mobileterminal which is scheduled per CDM group.

Regarding the first set of CDM groups, the co-scheduling informationallows the mobile terminal to benefit from an improved interferencecancellation. The improved interference cancellation may, however, onlybecome necessary if there is more than a given number (referred to asnumber X in FIGS. 3-6 ), say more than one (e.g., two or three) mobileterminals assigned different DMRS ports of a same CDM group of the firstset.

Instead, it there are less than the given number, say one or none,mobile terminals assigned to different DMRS ports of the same CDM groupof the first set, then, it may be sufficient to expect that the existingmechanisms are operating sufficient to establish the orthogonal DMRSports.

For example, in a 3GPP NR deployment scenario, the interferencecancellation is improved by utilizing a blind interference detectionmechanism in the receiver of the reference signals. Thereby without anyprior knowledge of the interference at the receiver (the co-schedulinginformation only indicates that there is interference from a givennumber, say two or three, mobile terminals) an improvement in thereception properties of the reference signals is attained.

Since the blind interference detection mechanism is computationallycomplex, costly on the power consumption and introduces a non-negligibleamount of processing delay into the signaling flow, this however is onlyadvantageous if there is (actually) a high amount of interferenceindicated. For this purpose, the number (referred to as number X inFIGS. 3-6 ) for which co-scheduling interference is indicated in thefirst set of CDM groups of is different from the number for whichco-scheduling interference is indicated in the second set of CDM groups.

In other words, the interpretation of the co-scheduling information maydepend on the CDM group and accordingly the set of CDM groups for whichit is received. If it is received for a CDM groups of the first set, inwhich its “own” reference signals are carried, then the co-schedulinginformation may indicate the presence of a given number of co-scheduledmobile terminals per CDM group as compared with CDM groups of the secondset, where the co-scheduling information may indicate the presence ofany co-scheduled mobile terminals per CDM group.

Similar to the above, the present disclosure also provides a basestation 260 for transmitting and/or receiving data to/from a mobileterminal 210 which uses multiple antennas in a mobile communicationsystem. Also, here the base station 260 and the mobile terminal 210 areconfigured to transmit and/or receive the data over a wireless channel250.

The base station 260 comprises circuitry, for example transceiver 270and processor 280, which, in operation, transmits, to the mobileterminal 210, a parameter defining a configuration for assigning toports respective resources for carrying reference signals, the resourcesbeing grouped in a plurality of code division multiplexing, CDM, groups,and transmits, to the mobile terminal 210, control informationindicating one of the set of layer-to-port mapping combinations which isto be applied for arranging reference signals on ports of at least oneCDM group for data transmission and/or reception,

Additionally, also here the control information are indicating aco-scheduling information for at least one and/or at least a differentCDM group of the plurality of CDM groups for the same data transmissionand/or reception.

Referring now to the form in which the control information iscommunicated between the base station 260 and the mobile station 210.For this purpose, reference is made to the FIGS. 3-6 as exemplaryimplementations of the signaling mechanism.

As already discussed before, control information (column 1 of eachfigure) is structured such that it not only indicate, to the mobileterminal 210, the one of the set of layer-to-port mapping configurations(columns 2 and 3 of each figure), but also indicates, to the mobileterminal 210, a co-scheduling information (columns 4 and 5 or 4 to 6 ofeach figure) on a per CDM group basis.

In this respect, a mobile terminal 210, having received a controlinformation, for example in binary form, refers to the row with thecorresponding index (in column 1 of each figure) and thus obtains, thelayer-to-port mapping which is being indicated by the base station, andalso the co-scheduling information for each of the CDM groups. As can beseen from the figures, it is suggested for the control information toallow separate (multiple) rows with same port-to-layer mappings in orderto reflect all possible permutations of co-scheduling information.

In more detail, FIG. 3 shows an exemplary set of layer-to-port mappingcombinations (columns 2 and 3) combined with co-scheduling information(columns 4 and 5) on a per CDM group basis for a DMRS configuration type1, and 1-symbol DMRS configuration. This example accordingly is based onthe assignment of DMRS ports to resources as shown in FIG. 1A, where atotal of two DMRS ports can be scheduled in each of two CDM groups.

Similarly, FIG. 4 shows an exemplary set of layer-to-port mappingcombinations (columns 2 and 3) combined with co-scheduling information(columns 4 and 5) on a per CDM group basis for a DMRS configuration type1, and 2-symbol DMRS configuration. This example accordingly is based onthe assignment of DMRS ports to resources as shown in FIG. 1B, where atotal of four DMRS ports can be assigned in each of two CDM groups.

Further, FIG. 5 shows an exemplary set of layer-to-port mappingcombinations (columns 2 and 3) combined with co-scheduling information(columns 4 to 6) on a per CDM group basis for the case of a DMRSconfiguration type 2, and 1-symbol DMRS. This example accordingly isbased on the assignment of DMRS ports to resources as shown in FIG. 1C,where a total number of two DMRS ports can be assigned in each of threeCDM groups.

Further, FIGS. 6 a and 6 b show exemplary set of layer-to-port mappingcombinations (columns 2 and 3) combined with co-scheduling information(columns 4 to 6) on a per CDM group basis for the case of a DMRSconfiguration type 2, and 2-symbol DMRS. This example accordingly isbased on the assignment of DMRS ports to resources as shown in FIG. 1D,where a total of four DMRS ports can be scheduled in each of three CDMgroups.

For all the exemplary implementation of the FIGS. 3-6 , it is assumedthat the CDM groups and DMRS ports are indexed in the following manner:

-   1. The CDM groups are consecutively indexed, and the DMRS ports of    the CDM groups are (also) consecutively indexed, namely such that    the indexes of the DMRS ports increases with indexes of the    plurality of CDM groups.

In other words, considering a (single) CDM group, the indexes of theDMRS ports of this CDM group are distributed consecutively. This canalready be inferred from the fact that the DMRS ports for each of theCDM groups, irrespective of the specific CDM group, are consecutivelyindexed.

Considering now separate CDM groups, the indexes of DMRS ports aredistributed into the CDM groups such that any one of the DMRS port(s),of a specific CDM group with a lower index, has a lower index than anyone of the DMRS port(s) of another specific CDM group with a next higherindex.

Having specified the indexing of the CDM groups and DMRS ports in anconsecutive manner, it is also assumed, with regard to the exemplaryimplementation of the FIGS. 3-6 , that the base station is assigning theDMRS ports to mobile station consecutively and increasingly (orsequentially) over all of the plurality of CDM groups.

-   2. Mobile terminals are assigned DMRS ports from among all of the    plurality of CDM groups having consecutive indexes starting with the    DMRS port with the lowest index.

Assuming, for the sake of argument, a base station 260 assigns to amobile terminal 210 the DMRS port with the lowest index (DMRS port 0, orP0). Then, should the base station 260 want to assign to the same mobileterminal 210, another DMRS port, it must proceed with assigning the DMRSport with the next higher consecutive index (DMRS port 1, or P1). Thus,it is not possible for one mobile terminal to be assigned two DMRS portswhich do not have consecutive indexes.

Reducing the total number of rows that can be indexed as controlinformation reduces the total amount of signaling overhead in thecontrol signal. Particularly, the inventors have recognized thesignaling of control information may be most efficient and effectivewhen the following rules are obeyed:

-   3. The maximum number of DMRS ports that can be scheduled per mobile    terminal in MU-MIMO is restricted to a given number, for instance,    to a number which is lower than the maximum number DMRS ports    defined by the configuration for assigning to ports respective    resources.

By reducing on the one hand the maximum number of DMRS ports per mobileterminal in MU-MIMO, the total number of permutations which arereflected in the control information, indicating the layer-to-portmapping as well as the co-scheduling on a per CDM group basis,drastically reduces.

Should, on the other hand control information allow indicating, withreference to the layer-to-port mapping, an exceeding number of DMRSports (higher than the maximum number of DMRS ports in MU-MIMO), thenthe mobile terminal can assume it is operating in SU-MIMO for the datatransmission and/or reception.

In the later case, from the mere fact that SU-MIMO is configured, thereis no necessity to additionally indicate co-scheduling informationregarding any of the CDM groups. Consistent therewith, the controlinformation then, for example, indicates the absence of anyco-scheduling.

For example, this is shown in FIG. 3 for the control informationcorresponding to index 11 (control information=“1011”) and correspondingto index 12 (control information=“1100”). There, despite of the maximumnumber of DMRS ports per mobile terminal in MU-MIMO being 2, three DMRSports (ports P0-P2) or four DMRS ports (ports (P0-P4) are indicated.Accordingly, the mobile terminal knows that the data transmission and/orreception are performed in SU-MIMO. Thus, there is no co-scheduling,hence, resulting in the co-scheduling information “0” for the CDM group0 and “0” for the CDM group 1.

-   4. The maximum number of DMRS ports which can be scheduled per    mobile terminal in SU-MIMO is restricted to a given number, for    instance, to a number which is lower than the maximum number of DMRS    ports defined by the configuration for assigning to ports respective    resources.

By reducing the maximum number of DMRS ports per mobile terminal inSU-MIMO, the total number of permutations which are reflected in thecontrol information, indicating the layer-to-port mapping as well as theco-scheduling on a per CDM group basis, further reduces.

For example, this is shown in FIG. 5 , where despite the availability ofa total of eight DMRS ports (ports P0-P7), the indexes of the controlinformation terminate with number 22 (control information=“10110”)relating to “only” four ports (ports P0-P3) that are being operated inSU-MIMO.

Please note that in FIGS. 4 and 6 a/b, there is not SU-MIMO mode ofoperation that can be configured, since the maximum number of ports permobile terminal in MU-MIMO and in SU-MIMO are equal, thus givingprecedence to MU-MIMO for the indication of the co-schedulinginformation.

-   5. A mobile terminal which is assigned all DMRS ports of a (single)    CDM group will not expect co-scheduling in the same CDM group.

This also reduces the number of permutations which are reflected in thecontrol information indicating the layer-to-port mapping as well as theco-scheduling on a per CDM group basis.

For example, this is shown in FIG. 3 , where for the control informationcorresponding to index 8 (control information “1000”) and to index 9(control information “1001”), all two DMRS ports (ports P0-P1) in CDMgroup 0 are assigned to mobile terminal itself such that nothing elsebut the co-scheduling information “0” is indicated for this CDM group 0.

-   6. A mobile terminal which is not assigned the DMRS port with the    lowest index of a (single) CDM group will expect co-scheduling in    the same CDM group and in CDM groups with a lower index.

This signaling of co-scheduling information for a CDM group exploits thefact that the DMRS ports are being assigned in a consecutive andincreasing manner (as discussed under Nr. 2 above).

Assuming, for the sake of argument, a base station 260 assigns to amobile terminal 210 the DMRS port with an intermediate index (DMRS port1, or P1), not a DMRS port with the lowest index (DMRS port 0, or P0).Then, since the base station 260 is required to assign the DMRS portsstarting with the lowest index, the mobile terminal 210 can infer, thatthere is a co-scheduled (other) mobile terminal in the same CDM group towhich the assigned DMRS port with index 1 belongs. Thus, it is inherentthat the co-scheduling information indicated by the control informationin MU-MIMO is always “1” in the same CDM group.

For example, this is shown in FIG. 3 , where for the control informationcorresponding to index 3 (control information=“0011”), and correspondingto index 4 (control information=“0100”), the indicated co-schedulinginformation is always “1” in the CDM group 0. Thus, also with this rule,the total number of permutations is reduced.

This inherent signaling of co-scheduling information holds true not onlyfor the CDM group to which the assigned DMRS port(s) belong(s), but alsoextends to those CDM groups which have a lower index.

Assuming, for the sake of argument, a base station 260 assigns to amobile terminal 210 the DMRS port with an intermediate index (DMRS port3, or P3), not a DMRS port with the lowest index (DMRS port 0, or P0).Then, since the base station 260 is required to assign the DMRS portsstarting with the lowest index, the mobile terminal 210 can infer, thatthere is a co-scheduled (other) mobile terminal in the same CDM group 1to which the assigned DMRS port with index 3 belongs, and also in theCDM group 0. Thus, the co-scheduling information indicated for the CDMgroup 0 and CDM group 1 by the control information in MU-MIMO is always“1”.

For example, this is shown in FIG. 3 , where for the control informationcorresponding to index 7 (control information=“0111”), the indicatedco-scheduling information is always “1” in the CDM group 0 and the CDMgroup 1. Thus, also with this rule, the total number of permutations isreduced.

The present disclosure can be realized by software, hardware, orsoftware in cooperation with hardware. Each functional block used in thedescription of each embodiment described above can be partly or entirelyrealized by an LSI such as an integrated circuit, and each processdescribed in the each embodiment may be controlled partly or entirely bythe same LSI or a combination of LSIs. The LSI may be individuallyformed as chips, or one chip may be formed so as to include a part orall of the functional blocks. The LSI may include a data input andoutput coupled thereto. The LSI here may be referred to as an IC, asystem LSI, a super LSI, or an ultra LSI depending on a difference inthe degree of integration.

However, the technique of implementing an integrated circuit is notlimited to the LSI and may be realized by using a dedicated circuit, ageneral-purpose processor, or a special-purpose processor. In addition,a FPGA (Field Programmable Gate Array) that can be programmed after themanufacture of the LSI or a reconfigurable processor in which theconnections and the settings of circuit cells disposed inside the LSIcan be reconfigured may be used. The present disclosure can be realizedas digital processing or analogue processing. If future integratedcircuit technology replaces LSIs as a result of the advancement ofsemiconductor technology or other derivative technology, the functionalblocks could be integrated using the future integrated circuittechnology. Biotechnology can also be applied.

According to a first aspect, a mobile terminal is suggested fortransmitting and/or receiving data in layers to/from a base stationusing multiple antennas in a mobile communication system, comprisingcircuitry which, in operation, receives, from the base station, aparameter defining a configuration for assigning to ports respectiveresources for carrying reference signals, the resources being grouped ina plurality of code division multiplexing, CDM, groups, and receivesfrom the base station, control information indicating one of the set oflayer-to-port mapping combinations which is to be applied for arrangingreference signals on ports of at least one CDM group for datatransmission and/or reception, wherein the control information areadditionally indicating a co-scheduling information for the at least oneand/or at least a different CDM group of the plurality of CDM groups forthe same data transmission and/or reception.

According to a second aspect, which can be combined with the firstaspect, the control information indicates the co-scheduling informationfor all or subset of the plurality of CDM groups.

According to a third aspect, which can be combined with the first orsecond aspect, the co-scheduling information indicates that the basestation is co-scheduling a different mobile terminal in the at least oneand/or different CDM group.

According to a fourth aspect, which can be combined with the first orsecond aspect, the co-scheduling information indicates that the basestation is co-scheduling at least a number of different mobile terminalsin the at least one and/or different CDM group.

According to the fifth aspect, which can be combined with the first tofourth aspect, the co-scheduling information is binary informationindicating the presence or absence of co-scheduling in each of theplurality of CDM groups.

According to a sixth aspect, which can be combined with the first tofifth aspect, the plurality of CDM groups are consecutively indexed andthe ports of each of the plurality of CDM groups are consecutivelyindexed, such that the indexes of the ports increases with the indexesof plurality of CDM groups.

According to a seventh aspect, which can be combined with the first tosixth aspect, the co-scheduling information indicates co-scheduling onlyfor those of the plurality of CDM groups having an index correspondingto or higher than the at least one CDM group.

According to a eighth aspect, which can be combined with the first toseventh aspect, the resources assigned to ports of a CDM group, havingthe index lower than the lowest index of the ports indicated in thecontrol information for arranging the reference signals, are inherentlyknown to be co-scheduled by the base station.

According to a ninth aspect, which can be combined with the first toeighth aspect the mapping implies indexing the layer-to-port mappingcombinations and the co-scheduling information.

According to a tenth aspect, which can be combined with the first toninth aspect, the resources assigned to the ports include two resourcecomponent configurations, a first resource component configurationincluding a comb and a cyclic shift of reference signals, the combconsisting either of subcarriers with an odd subcarrier index or ofsubcarriers with an even subcarrier index, a second resource componentconfiguration including frequency division multiplexing and a frequencydivision orthogonal cover code, OCC, and the circuitry, in operation,further receives, from the base station, an indicator indicating whetherthe first resource component configuration or the second resourcecomponent configuration is used.

According to an eleventh aspect, which can be combined with the first totenth aspect, the parameter defining the configuration for assigning toports respective resources for carrying reference signals is receivedvia a Radio Resource Control, RRC, protocol.

According to a twelfth aspect, which can be combined with the first toeleventh aspect, wherein the control information indicating the one ofthe set of layer-to-port mapping combinations and indicating theco-scheduling information is received via a physical downlink controlchannel, PDCCH.

According to a thirteenth aspect, which can be combined with the firstto twelfth aspect, the reference signals are front loaded demodulationreference signals.

According to a fourteenth aspect, which can be combined with the firstto thirteenth aspect, the mobile terminal further comprises atransceiver which, in operation, performs the data transmission and/orreception applying the indicated layer-to-port mapping combination.

According to a fifteenth aspect, which can be combined with the first tofourteenth aspect, the mobile terminal further comprises a processorwhich in operation performs interference compensation on the receivedreference signals and/or rate matching for the data transmission and/orreception.

According to a sixteenth aspect, a method is suggested to be performedby a mobile terminal for transmitting and/or receiving data in layersto/from a base station using multiple antennas in a mobile communicationsystem, comprising the steps of: receiving, from the base station, aparameter defining a configuration for assigning to ports respectiveresources for carrying reference signals, the resources being grouped ina plurality of code division multiplexing, CDM, groups, and receivingfrom the base station, control information indicating one of the set oflayer-to-port mapping combinations which is to be applied for arrangingreference signals on ports of at least one CDM group for datatransmission and/or reception, wherein the control information areadditionally indicating a co-scheduling information for the at least oneand/or at least a different CDM group of the plurality of CDM groups forthe same data transmission and/or reception.

According to a seventh aspect, which can be combined with the sixteenthaspect, the control information indicates the co-scheduling informationfor all or subset of the plurality of CDM groups.

According to an eighteenth aspect, which can be combined with thesixteenth or seventeenth aspect, the co-scheduling information indicatesthat the base station is co-scheduling a different mobile terminal inthe at least one and/or different CDM group.

According to a nineteenth aspect, which can be combined with thesixteenth or seventeenth aspect, the co-scheduling information indicatesthat the base station is co-scheduling at least a number of differentmobile terminals in the at least one and/or different CDM group.

According to a twentieth aspect, which can be combined with thesixteenth to nineteenth aspect, the co-scheduling information is binaryinformation indicating the presence or absence of co-scheduling in eachof the plurality of CDM groups.

According to a twenty first aspect, which can be combined with thesixteenth to twentieth aspect, the plurality of CDM groups areconsecutively indexed, and the ports of each of the plurality of CDMgroups are consecutively indexed, such that the indexes of the portsincreases with the indexes of plurality of CDM groups.

According to a twenty second aspect, which can be combined with thesixteenth to twenty first aspect, the co-scheduling informationindicates co-scheduling only for those of the plurality of CDM groupshaving an index corresponding to or higher than the at least one CDMgroup.

According to a twenty third aspect, which can be combined with thesixteenth to twenty second aspect, the resources assigned to ports of aCDM group, having the index lower than the lowest index of the portsindicated in the control information for arranging the referencesignals, are inherently known to be co-scheduled by the base station.

According to a twenty fourth aspect, which can be combined with thesixteenth to twenty third aspect, the mapping implies indexing thelayer-to-port mapping combinations and the co-scheduling information.

According to a twenty fifth aspect, which can be combined with thesixteenth to twenty fourth aspect, the resources assigned to the portsinclude two resource component configurations, a first resourcecomponent configuration including a comb and a cyclic shift of referencesignals, the comb consisting either of subcarriers with an oddsubcarrier index or of subcarriers with an even subcarrier index, asecond resource component configuration including frequency divisionmultiplexing and a frequency division orthogonal cover code, OCC, andthe method comprises the further step of receiving, from the basestation, an indicator indicating whether the first resource componentconfiguration or the second resource component configuration is used.

According to a twenty sixth aspect, which can be combined with thesixteenth to twenty fifth aspect, the parameter defining theconfiguration for assigning to ports respective resources for carryingreference signals is received via a Radio Resource Control, RRC,protocol.

According to a twenty seventh aspect, which can be combined with thesixteenth to twenty sixth aspect, the control information indicating theone of the set of layer-to-port mapping combinations and indicating theco-scheduling information is received via a physical downlink controlchannel, PDCCH.

According to a twenty eighth aspect, which can be combined with thesixteenth to twenty seventh aspect, the reference signals are frontloaded demodulation reference signals.

According to a twenty ninth aspect, which can be combined with thesixteenth to twenty eighth aspect, the method comprises the further stepof performing the data transmission and/or reception applying theindicated layer-to-port mapping combination.

According to a thirtieth aspect, which can be combined with thesixteenth to twenty ninth aspect, the method comprises the further stepof performs interference compensation on the received reference signalsand/or rate matching for the data transmission and/or reception.

According to a thirty first aspect, a base station is suggested fortransmitting and/or receiving data in layers to/from a mobile terminal(210) using multiple antennas in a mobile communication system,comprising: circuitry (270; 280) which, in operation, transmits, to themobile terminal, a parameter defining a configuration for assigning toports respective resources for carrying reference signals, the resourcesbeing grouped in a plurality of code division multiplexing, CDM, groups,and transmits, to the mobile terminal, control information indicatingone of the set of layer-to-port mapping combinations which is to beapplied for arranging reference signals on ports of at least one CDMgroup for data transmission and/or reception, wherein the controlinformation are additionally indicating a co-scheduling information forthe at least one and/or at least a different CDM group of the pluralityof CDM groups for the same data transmission and/or reception.

According to a thirty second aspect, a method to be performed by a basestation is suggested for transmitting and/or receiving data in layersto/from a mobile terminal using multiple antennas in a mobilecommunication system, comprising the steps of: transmitting, to themobile terminal, a parameter defining a configuration for assigning toports respective resources for carrying reference signals, the resourcesbeing grouped in a plurality of code division multiplexing, CDM, groups,and transmitting, to the mobile terminal, control information indicatingone of the set of layer-to-port mapping combinations which is to beapplied for arranging reference signals on ports of at least one CDMgroup for data transmission and/or reception, wherein the controlinformation are additionally indicating a co-scheduling information forthe at least one and/or at least a different CDM group of the pluralityof CDM groups for the same data transmission and/or reception.

The various embodiments described above can be combined to providefurther embodiments. All of the U.S. patents, U.S. patent applicationpublications, U.S. patent applications, foreign patents, foreign patentapplications and non-patent publications referred to in thisspecification and/or listed in the Application Data Sheet areincorporated herein by reference, in their entirety. Aspects of theembodiments can be modified, if necessary to employ concepts of thevarious patents, applications and publications to provide yet furtherembodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

The invention claimed is:
 1. An integrated circuit for controlling auser equipment, the integrated circuit comprising control circuitrywhich, in operation, receives, from a base station, a parameter defininga configuration for assigning to ports respective resources for carryingreference signals, the resources being grouped in a plurality of codedivision multiplexing (CDM) groups, and receives from the base station,control information indicating one of a set of layer-to-port mappingcombinations which is to be applied for arranging reference signals onports of at least one CDM group for data transmission and/or reception,wherein the control information additionally indicates co-schedulinginformation for the at least one and/or at least a different CDM groupof the plurality of CDM groups for the same data transmission and/orreception, wherein the plurality of CDM groups are consecutively indexedand wherein the ports of each of the plurality of CDM groups areconsecutively indexed, such that the indexes of the ports increase withthe indexes of the plurality of CDM groups.
 2. The integrated circuitaccording to claim 1, wherein the control information indicates theco-scheduling information for all or a subset of the plurality of CDMgroups.
 3. The integrated circuit according to claim 1, wherein theco-scheduling information indicates that the base station isco-scheduling a different user equipment in the at least one and/ordifferent CDM group.
 4. The integrated circuit according to claim 1,wherein the co-scheduling information indicates that the base station isco-scheduling at least a number of different user equipments in the atleast one and/or different CDM group.
 5. The integrated circuitaccording to claim 1, wherein the co-scheduling information is binaryinformation indicating the presence or absence of co-scheduling in eachof the plurality of CDM groups.
 6. The integrated circuit according toclaim 1, wherein the co-scheduling information indicates co-schedulingonly for those of the plurality of CDM groups having an indexcorresponding to or higher than the at least one CDM group.
 7. Theintegrated circuit according to claim 1, wherein the resources assignedto ports of a CDM group, having the index lower than the lowest index ofthe ports indicated in the control information for arranging thereference signals, are inherently known to be co-scheduled by the basestation.
 8. The integrated circuit according to claim 1, wherein themapping implies indexing the layer-to-port mapping combinations and theco-scheduling information.
 9. The integrated circuit according to claim1, wherein the resources assigned to the ports include two resourcecomponent configurations, a first resource component configurationincluding a comb and a cyclic shift of reference signals, the combconsisting either of subcarriers with an odd subcarrier index or ofsubcarriers with an even subcarrier index, a second resource componentconfiguration including frequency division multiplexing and a frequencydivision orthogonal cover code (OCC), and the control circuitry, inoperation, further receives, from the base station, an indicatorindicating whether the first resource component configuration or thesecond resource component configuration is used.
 10. The integratedcircuit according to claim 1, wherein the parameter defining theconfiguration for assigning to ports respective resources for carryingreference signals is received via a Radio Resource Control (RRC)protocol.
 11. The integrated circuit according to claim 1, wherein thecontrol information indicating the one of the set of layer-to-portmapping combinations and indicating the co-scheduling information isreceived via a physical downlink control channel (PDCCH).
 12. Theintegrated circuit according to claim 1, wherein the reference signalsare front loaded demodulation reference signals.
 13. The integratedcircuit according to claim 1, further comprising transceiver circuitrywhich, in operation, performs the data transmission and/or receptionapplying the indicated layer-to-port mapping combination.
 14. Theintegrated circuit according to claim 1, further comprising processingcircuitry which, in operation, performs interference compensation on thereceived reference signals and/or rate matching for the datatransmission and/or reception.